This invention broadly relates to a method of forming a silicon oxide film by the use of plasma CVD (Chemical Vapor Deposition) apparatus, and a forming apparatus thereof.
More specifically, this invention relates to a method of forming a silicon oxide film by the CVD method using plasma CVD apparatus in which a plasma formation region and a substrate process (deposition) region are separated to each other.
Recently, suggestion has been made about a remote plasma CVD apparatus as a plasma CVD apparatus for depositing a film on a substrate on the condition that a plasma damage is suppressed.
In such a remote plasma CVD apparatus, a plasma formation region and a substrate process (deposition) region generally are separated to each other.
This CVD apparatus is becoming increasingly important in a process for manufacturing a semiconductor device to achieve both high reliability and high performance.
For example, disclosure has been made about a parallel plate remote plasma CVD apparatus as the remote plasma CVD apparatus for a large-scale substrate in Japanese Unexamined Patent Publication (JP-A) No. Sho. 53-91665 (hereinafter, will be referred to as a conventional example).
The large-scale substrate is generally used in a process for forming a switching transistor of a flat panel display having a large area, a process for forming a driving circuit transistor, and a silicon wafer process for a wafer having a large diameter.
Such a parallel plate remote plasma CVD apparatus is illustrated in FIG. 1, and is provided with a plasma sealing electrode 80 having a plurality of penetrations (namely, radical passing holes 50) between a substrate susceptor 20 and a high-frequency applying electrode 10 in the conventional parallel plate plasma CVD apparatus. Herein, a substrate 30 is arranged on the susceptor 20 while the plasma sealing electrode 80 has a hollow structure.
With this structure, plasma 60 of a first gas 100 is sealed between the plasma-sealing electrode 80 and the high-frequency applying electrode 10.
Under such a circumstance, the plasma is uniformly generated by the use of the parallel plates with a large area. Consequently, the radicals necessary to the deposition process are uniformly supplied in the large area.
In such a conventional example, a second gas, which is not decomposed with plasma, is supplied via neutral gas injection holes 90 (or spraying holes) on the condition that the second gas is uniformly distributed along an electrode surface. In consequence, the deposition process due to reaction with diffused radicals can be uniformly carried out along the large area.
Subsequently, description will be made about a method for depositing the silicon oxide film on the substrate by the use of the conventional parallel plate remote plasma CVD apparatus illustrated in FIG. 1.
First, oxygen gas is supplied to the plasma generation region as the first gas 100, and the high-frequency power is applied to the high-frequency applying electrode 10 to generate oxygen plasma 60.
This oxygen plasma 60 is sealed between the plasma sealing electrode 80 and the high-frequency applying electrode 10. Thereby, only excitation oxygen atoms, excitation oxygen molecules, oxygen atoms, oxygen molecules and ozone are supplied to the deposition region via the radical passing holes 50. In this case, oxygen ions and electrons almost are not supplied thereto.
In the meantime, monosilane gas as the second gas 110 is supplied into the plasma-sealing electrode 80 having the hollow structure.
The monosilane gas is supplied from the neutral gas injection holes 90 which are opened on the substrate side surface of the plasma-sealing electrode 80.
With this structure, the monosilane gas reacts with the excitation oxygen atoms, the excitation oxygen molecules, the oxygen atoms, the oxygen molecules and the ozone in vapor phase between the plasma-sealing electrode 80 and the substrate 30.
As a result of the reaction, silicon oxide precursors, such as SiHx, SiHxOy, and SiOy are produced. The precursors are attached on the substrate 30, and oxidation reaction or thermal dissociation is carried out on a growth surface on the substrate 30 to deposit the silicon oxide film on the substrate 30.
The radical passing holes 50 and the neutral gas injection holes 90 are uniformly distributed along the plane on the plasma-sealing electrode 80. Consequently, flax plane distribution of gas supplied from the respective holes will readily become uniform.
Accordingly, vapor phase reaction uniformly occurs in the plane on the substrate, and the silicon oxide precursors are uniformly distributed in the plane on the substrate 30. As a result, film distribution of the silicon oxide film formed on the substrate 30 also becomes uniform in the plane.
Thus, great attention has been given to the parallel plate remote plasma CVD as a method for depositing the silicon oxide film or a silicon nitride film serving as a gate insulating film of a thin-film transistor (TFT) formed on a large glass substrate, an amorphous silicon film serving as an active layer or a gate electrode of the thin-film transistor formed on the large-area glass substrate, and the silicon oxide film or the silicon nitride film serving as an interlayer insulating film of a transistor device formed on a large-area silicon substrate.
This is because a thin-film having excellent uniformity in a substrate plane can be deposited on the condition that the plasma damage is suppressed in the parallel plate remote plasma CVD.
Further, the remote plasma CVD apparatus has another advantages. Specifically, existing density of ion or electrons can be ignored in the deposition region. In consequence, reaction in the vapor phase relatively becomes simple.
Moreover, quantity of reaction species, such as, oxygen atom excitation species and oxygen molecular excitation species or quantity of an intermediate generating species formed in the vapor phase, such as SiHx, SiHxOy, and SiOy can be controlled.
However, a specific species is particularly not identified and measured so as to control the quantity thereof in the conventional example.
In the conventional example, the control of the species quantity is estimated based on experience. As a result of the estimation, adjustment must be about CVD deposition conditions, such as, pressure, plasma excitation power, gas flow rate, and gas composition.
Thus, the advantage of the remote plasma CVD apparatus, which can control the quantity of the reaction species and the intermediate generating species, is not utilized at maximum in the conventional example. As a result, the silicon oxide film can not be formed with high quality in the conventional example.